The proposed research constitutes the second step toward our goal of creating a completely implanted drug-delivery system for the automatic control of blood pressure. The first step has been completed and demonstrated that arterial pulse-wave velocity (PWV) tracks diastolic pressure faithfully, thereby eliminating the need for an implantable pressure transducer. The research proposed herein is designed to demonstrate that PWV can reliably indicate blood pressure in the chronic normo- and hypertensive animal. The studies to be conducted will employ large dogs with implanted electrodes to detect the pulse by measurement of the impedance decrease between a pair of periarterial electrodes. Four pairs of electrodes will be implanted to examine the appropriateness of different sites for pulse sensing. The three best arterial sites will be selected for the chronic studies of the relationship between PWV and blood pressure. We have already developed an algorithm that measures the beat-by-beat time difference between two arterial pulses and scales this time to PWV. Blood pressure and PWV will be correlated in normotensive and hypertensive animals, with exercise to increase blood pressure. In addition, the animals will be sedated and correlations will be made using drugs to raise and lower blood pressure. Finally, in those animals that are to be sacrificed for the electrode-maturation studies, correlations will be made over a wider range of pressure using drugs. In all studies, we will show that PWV (actually the reciprocal of pulse transit time) tracks diastolic pressure, and therefore can serve as an adequate signal for controlling and automatic implanted blood-pressure controller.